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Validation of a Coupled Multizone-CFD Program for Building Airflow and Contaminant Transport Simulations
Abstract
Current multizone airflow network models assume air momentum effects, contaminant concentrations, and air temperatures are uniformly and homogeneously distributed in a zone of a building. These assumptions can cause errors for zones where air and/or contaminant are not well mixed. A coupled multizone-CFD program has been developed to improve the multizone model by applying a CFD model to those poorly mixed zones and the multizone model to the remaining zones. This paper validates the coupled multizone-CFD program by using experimental data obtained in a four-zone facility with nonuniform distributions of air momentum effects, contaminant concentrations, and air temperatures. The calculated results by the coupled program generally agreed with the experimental data although discrepancies exist in some cases. The coupled multizone-CFD simulations used less computing time than the CFD simulations for the whole flow domain.
... However, because CONTAM adopts the lumped system approach under the assumption that the pressure and temperature of each zone (room) are uniform and air motion is neglected, the effect of airflow is not properly considered. Wang et al. [12] presented an experimental multizone model that can be used to validate computational fluid dynamics (CFD) for indoor flow analysis, highlighting the limitations of CONTAM. Tian et al. [13] proposed an algorithm that couples fast fluid dynamics (FFD) and CONTAM to solve problems arising from the well-mixed assumptions of CONTAM. ...
... where des i U = 0 which is no-slip boundary condition and des T is desired temperature on block surface. (12) where ( ) i u x and ( ) T x are fluid velocity and temperature at the Eulerian grid point x , respectively. For the distribution of force and heat source on the Lagrangian point to the Eulerian grid point, the same weight is used as follows ...
... To validate the results of the LES for indoor flow analysis in a multizone environment and investigate the flow characteristic, we chose two experimental models [12], as shown in Fig. 2. In the first model ( Fig. 2(a)), the airflow from zone 1 to the other connected zones is driven by the pressure difference and momentum of the supply airflow. In the second model ( Fig. 2(b)), unbalanced airflows arise from the buoyancy effect generated by a block with heat in zone 2. For both models, the computational domain was 6.25 m × 2.45 m × 4.95 m along the x, y and z directions, respectively. ...
We used large-eddy simulation (LES) to numerically simulate two differently driven indoor airflows occurring in a multizone environment. In the first case, air flowed from one zone to another through a small hole driven by the total pressure difference. In the second case, unbalanced airflows arose from the buoyancy effect, which was generated by a heat source present in a specific location. To validate the LES prediction for the indoor flow analysis, we compared our simulation results with the chamber facility experimental results and other simulation results. Based on this validation, we confirmed that the LES reliably simulates indoor airflow. In addition, we discussed the flow characteristics and investigated the feasibility of modeling the flow rate through openings using an orifice formula.
... Case studies had been carried out to use the developed model to study common indoor airflow types such as forced convection, natural convection and contaminant transportation in a building (Yuan 2003;Tan and Glicksman 2005). Wang and Chen (2007) further validated the dynamic coupling strategy by using experiments in which stratified airflows were involved including the nonuniform distribution of momentum, temperature, and contaminant (Wang and Chen 2007;Srebric et al. 2008). ...
... Case studies had been carried out to use the developed model to study common indoor airflow types such as forced convection, natural convection and contaminant transportation in a building (Yuan 2003;Tan and Glicksman 2005). Wang and Chen (2007) further validated the dynamic coupling strategy by using experiments in which stratified airflows were involved including the nonuniform distribution of momentum, temperature, and contaminant (Wang and Chen 2007;Srebric et al. 2008). ...
... where is the discharge coefficient normally ranging between 0.6 to 0.75; is the area size of the opening; is the density of the air; is constant, which is 0.5 for large openings. Δ is the pressure difference which is the aggregate sum of the total pressure difference , and pressure difference as a result of wind Δ , and pressure difference due to density and elevation difference Δ (Wang and Chen 2007). ...
Multizone models are widely used in building airflow and energy performance simulations due to their fast computing speed. However, multizone models assume that the air in a room is well mixed, consequently limiting their application. In specific rooms where this assumption fails, the use of computational fluid dynamics (CFD) models may be an alternative option. Previous research has mainly focused on coupling CFD models and multizone models to study airflow in large spaces. While significant, most of these analyses did not consider the coupled simulation of the building airflow with the building's Heating, Ventilation, and Air-Conditioning (HVAC) systems. This paper tries to fill the gap by integrating the models for HVAC systems with coupled multizone and CFD simulations for airflows, using the Modelica simulation platform. To improve the computational efficiency, we incorporated a simplified CFD model named fast fluid dynamics (FFD). We first introduce the data synchronization strategy and implementation in Modelica. Then, we verify the implementation using two case studies involving an isothermal and a non-isothermal flow by comparing model simulations to experiment data. Afterward, we study another three cases that are deemed more realistic. This is done by attaching a variable air volume (VAV) terminal box and a VAV system to previous flows to assess the capability of the models in studying the dynamic control of HVAC systems. Finally, we discuss further research needs on the coupled simulation using the models.
... Both models require knowledge of flow path descriptions, building geometry, weather and local shielding conditions, terrain roughness factors and mechanical ventilation system properties. Addressing the underlying assumption in most multizonal models, i.e., the assumption of well-mixed zones, and neglecting airflow momentum preservation, researchers proposed computational fluid dynamics (CFD), fast fluid dynamics, and combined multizone CFD methods [33][34][35][36][37][38] . One of the major drawbacks of using CFD methods is the simulation time, which makes CFD unfeasible for performing long-term dynamic simulations of a building with relatively complex structures. ...
... Computational fluid dynamics (CFD), fast fluid dynamics, and combined multizone CFD methods [33][34][35][36][37][38] All regions obey the law of conservation of mass, energy and momentum. ...
Air infiltration through building envelopes has a considerable impact on the comprehensive performance of buildings, especially in terms of their energy demand and indoor air quality. Therefore, it is important to accurately predict building air infiltration rates under various scenarios. High airtightness is one of the typical characteristics of passive ultra-low energy buildings. With the rapid application of passive technology in building energy efficiency, the airtightness of new urban buildings has been significantly improved. The centralized air leakage path distribution assumption of current prediction model for building air infiltration rate is inconsistent with the actual situation of high airtightness buildings, which reduces its prediction accuracy and application range. Therefore, it is of great practical significance and academic value to carry out the research on the prediction model of air infiltration rate of buildings with high airtightness.
This paper presents an air infiltration prediction model for single-zone buildings with adventitious openings. The building envelope was broken down into permeable parts and impermeable parts, and the air leakage pathways were assumed to be uniformly and continuously distributed in the permeable envelope. A linear pressure distribution over the building facade was assumed, and the airflow rate was integrated in the vertical and horizontal planes to theoretically predict the air infiltration rate. The feasibility of the proposed model was tested by comparing the air infiltration rates simulated by this model with those determined using the tracer gas attenuation method of an airtight building. The initial test results suggest that this model is mathematically robust and is capable of modeling the air infiltration of a building in a wide variety of scenarios. Reasonable agreement was found between the tested and simulated results. This study can provide basic theoretical support for the coupling performance analysis of high airtightness buildings.
... However, in the real world, occupants' activities and heat sources may all interrupt airflow patterns in the room, exerting an influence on zonal infiltrations. This could be investigated in future studies using the CFD capabilities of CONTAM [51,52]. ...
... However, this assumption may simplify the real exposures in buildings. There could be additional turbulent mixing that happens within and between internal zones in the building due to heat sources, movement of occupants, flows created by doors opening, etc. Differential exposure risks for individuals at different locations in the zone could be considered in future studies by utilizing the CFD capabilities of CONTAM [51,52]. ...
The world has faced tremendous challenges during the COVID-19 pandemic since 2020, and effective clean air strategies that mitigate infectious risks indoors have become much more essential. Not much information is available for reducing this risk in the whole-building multizone context. In this study, a novel approach based on the Wells-Riley model applied to a multizone building was proposed to simulate exposure to infectious doses in terms of “quanta”. This modeling approach quantifies the relative benefits of different risk mitigation strategies so that their effectiveness could be compared. A case study for the US Department of Energy large office prototype building was conducted to illustrate the approach. The infectious risk propagation from the infection source throughout the building was evaluated. Different mitigation strategies were implemented, including increasing outdoor air ventilation rates and adding air-cleaning devices such as MERV filters and portable air cleaners (PACs) with HEPA filters in-room/in-duct germicidal ultraviolet (UV) lights, layering with wearing masks. Results showed that to keep the risk of the infection propagating low the best strategy without universal masking was the operation of a very large industrial-sized air cleaner; whereas with masking all strategies were acceptable. This study contributes to a better understanding of the airborne transmission risks in multizone, mechanically ventilated buildings and the how to reduce infection risk from a public health perspective of different mitigation strategies.
... Building airtightness can be predicted in several ways [9]: by theoretical [10,11], empirical [12][13][14][15][16], building characteristic or single component models [17]. Theoretical models recognize a building as an aggregation of numerous cracks. ...
... Each crack can be modeled individually using Computational Fluid Dynamics (CFD). Nevertheless, these models are not suitable for practical use [10] because of the calculation time [11] and power necessary to obtain accurate and effective models. ...
Recently, the construction of external ventilated walls has become popular for public and office buildings. These blocks are used without internal rendering because of their good interior surface, stable dimensions and various filling of masonry joints, which provide an attractive architectural appearance. However, problems with the airtightness of such walls often occur. Currently, there are no standard methods to predict the airtightness of such wall. In practice, samples of particular walls are produced, and their air permeability is measured at laboratories. For the broader use of the results of laboratory air permeability measurements, a methodology has been developed to predict the air permeability of block masonry walls using experimentally determined air flow resistances of the individual layers. The masonry from various blocks were used for the research; mineral wool boards of various air permeability were used for thermal insulation and the wind protection layer. After measuring the air resistance of the samples, the air flow resistances of walls of different construction were calculated. This study compared the calculated and measured air permeability values of different wall masonry samples and evaluated the suitability of created calculation method for prediction of the airtightness of insulated block masonry wall.
... In coupled CONTAM and CFD0 program, CFD0 applies to the zone where the multizone assumption fails and CONTAM applies to the rest of the zones. Wang CFD0 programs with experimental data from a four-zone facility at Purdue University (27). The results indicated that the coupled program (CONTAM-CFD0) calculated more accurate airflow rates compared to CONTAM and used less computing time compared to CFD0. ...
... The results indicated that the coupled program (CONTAM-CFD0) calculated more accurate airflow rates compared to CONTAM and used less computing time compared to CFD0. Coupled CONTAM-CFD0 program reduced computational time up to one order of magnitude compared to CFD0 and was able to correctly predict the airflow and contaminant distribution in all zones (27). CFD0 is a CFD program originally developed for the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) project RP-927 (28) which is currently freely available through NIST. ...
Indoor air concentrations are susceptible to temporal and spatial variations and have long posed a challenge to characterize for vapor intrusion scientists, in part, because there was a lack of evidence to draw conclusions about the role that building and weather conditions played in altering vapor intrusion exposure risks. Importantly, a large body of evidence is available within the building science discipline that provides information to support vapor intrusion scientists in drawing connections about fate and transport processes that influence exposure risks. Modeling tools developed within the building sciences provide evidence of reported temporal and spatial variation of indoor air contaminant concentrations. In addition, these modeling tools can be useful by calculating building air exchange rates (AERs) using building specific features. Combining building science models with vapor intrusion models, new insight to facilitate decision-making by estimating indoor air concentrations and building ventilation conditions under various conditions can be gained. This review highlights existing building science research and summarizes the utility of building science models to improve vapor intrusion exposure risk assessments.
... For example, Younes and Abi Shdid [87] used the ASHRAE database to estimate the crack characteristics and distribution in their demonstration CFD model. Further to the use of CFD for estimating airtightness, CFD has long computation times and requires fairly significant computational power [84]. This makes it impractical for their use at this time, as also identified by Prignon and Moeseke [63] and others [84,87]. ...
... Further to the use of CFD for estimating airtightness, CFD has long computation times and requires fairly significant computational power [84]. This makes it impractical for their use at this time, as also identified by Prignon and Moeseke [63] and others [84,87]. ...
In this study, CONTAM 3.2, a modeling software that uses component air leakage rates, was used to estimate post-retrofit improvements in airtightness. A 12 storey residential building in Vancouver, British Columbia was studied. Pre- and post-retrofit airtightness data were used to assess the accuracy of the model predictions. Using a heuristic and two formal approaches, a pre-retrofit model was calibrated. Next, using the calibrated model and the specified airtightness data associated with the retrofit measures, post-retrofit airtightness was estimated using two approaches. Modelling results were then compared to the post-retrofit airtightness data. Using the factorial analysis and Monte Carlo approaches it was found that the best estimates were within 36% of the measured airtightness. While modeling can be an effective estimation tool, it is likely that the model developed here underestimated airtightness improvements because the retrofit measures were more airtight than specified by the designers. [Link to full text: http://hdl.handle.net/1807/89559]
... Hence, in order to simulate indoor air distributions with good physical accuracy and within an acceptable computing time, it is essential to develop a method that is faster than conventional CFD while maintaining the accuracy of the results. The most popular amongst the fast computational methods for predicting indoor air distributions, faster than CFD, are multizone network models (Wang and Chen 2007) and zonal models (Megri and Haghighat 2007). These models can give a reasonable approximation of bulk parameters and the influence of key parameters but are simplistic in their assumptions and hence suffer in terms of physical accuracy. ...
... Furthermore, these models are not easily adaptable and require special models and zones to be incorporated for every new building configuration. CFD simulations can be coupled with multizone (Wang and Chen 2007) models to improve accuracy for specific zones of interest, but at the expense of losing the advantage of fast computation time due to the CFD simulation's long computing time (Jin et al. 2012). More recently a fast fluid dynamics (FFD) method has been used to simulate indoor environments in real-time (Zuo and Chen 2009;). ...
A 3D time dependent interactive real-time thermal and turbulent fluid flow solver with an integrated visualisation tool has been implemented. Our work emphasises on accelerating or speeding-up the time to solution. A novel Lattice Boltzmann Method (LBM) -based CFD technique has been implemented on the graphics processing unit (GPU) for this purpose. Good agreement between LBM results and traditional CFD based method are observed.
... To address these issues, researchers have proposed coupling multi-zone network models with CFD calculations, validating this coupled approach using experimental data. This framework has been used to investigate the effectiveness of emergency ventilation in protecting building occupants during toxic gas releases [121,[125][126][127], simulate indoor airflow and temperature distribution [124], and improve building ventilation design [128]. Nonetheless, the coupling procedure is complex, requiring the prior establishment of the existence of the numerical solution. ...
Lightweight structures, characterized by rapid assembly, are vital for creating habitats in outdoor environments, but their implementation in high-plateau cold regions encounters significant challenges in heating and ventilation. This paper systematically introduces the environmental characteristics and reviews the demands and primary influencing factors of indoor environments in these regions. The advantages and limitations of underground lightweight construction are also discussed. Current research indicates that evaluation methods for air quality in high-altitude cold regions require further development. Reducing building heat loss and minimizing cold air infiltration can enhance indoor environments and lower energy consumption. However, it is essential to establish effective ventilation strategies to prevent the accumulation of air pollutants. Then, potential passive ventilation improvement measures suitable for the environmental characteristics of high-cold plateaus are outlined. The application potential and possible limitations of these measures are summarized, providing references for future research. Finally, the main research methods for ventilation and heating within building interiors are organized and discussed. Findings indicate that computational fluid dynamics models are predominantly used, but they demonstrate low efficiency and high resource consumption for medium- to large-scale applications. Integrating these models with network models can achieve a balance of high computational accuracy and efficiency.
... Another significant limitation is that while this model can calculate the performance of the entire building, it is unable to forecast the precise distribution of temperature and air velocity in the room because it assumes that each zone's pressure, temperature, and pollutant concentration will be uniform. [47]. Air is also considered stationary so that the air movement in the zone does not affect the results of air pressure, hence it is not suitable for representing real natural ventilation which has gradients of temperature, velocity, and air pressure (unsteady). ...
In this digital era, information technology really helps the process of designing and designing a more efficient, durable, high-performance building. After the pandemic, indoor air quality (IAQ) becomes an important issue since human spend most of the time indoor, which can impact their well-being in the long term. Ventilation is considered as one of the effective strategies in order to control IAQ. However, airflow and pollutant transport are a complex mechanism, therefore it is hard to understand only by experimental method. Advance information technology nowadays can help predict the building air quality from the early design stage. This paper aims to discuss various building simulation models and the popular software used. The basic principles of three models, multizone, zonal, and computational fluid dynamic (CFD) models are explained, following with their advantages and limitation. By comparing the simulation ability, accuracy, computational cost, simulation time, user skill requirement, and visual user interface, architect and researcher can choose the right simulation model according to their needs, in designing building which emit less pollutant and provide enough ventilation for contaminants discharge.
... In addition, flow patterns could be manipulated to maximally reduce quanta concentrations in occupants' breathing zone and promote the effectiveness of mitigation strategies. The computational fluid dynamics (CFD) is an effective method for predicting detailed indoor airflows, which has been developed for the CONTAM multizone modeling [48,49]. Utilizing the CFD capabilities of CONTAM, the pros and cons of different mechanical mitigation strategies would be better understood. ...
Airborne transmission of SARS-CoV-2 mostly occurs indoors, and effective mitigation strategies for specific building types are needed. Most guidance provided during the pandemic focused on general strategies that may not be applicable for all buildings. A systematic evaluation of infection risk mitigation strategies for different public and commercial buildings would facilitate their reopening process as well as post-pandemic operation. This study evaluates engineering mitigation strategies for five selected US Department of Energy prototype commercial buildings (i.e., Medium Office, Large Office, Small Hotel, Stand-Alone Retail, and Secondary School). The evaluation applied the multizone airflow and contaminant simulation software, CONTAM, with a newly developed CONTAM-quanta approach for infection risk assessment. The zone-to-zone quanta transmission and quanta fate were analyzed. The effectiveness of mechanical ventilation, and in-duct and in-room air treatment mitigation strategies were evaluated and compared. The efficacy of mitigation strategies was evaluated for full, 75%, 50% and 25% of design occupancy of these buildings under no-mask and mask-wearing conditions. Results suggested that for small spaces, in-duct air treatment would be insufficient for mitigating infection risks and additional in-room treatment devices would be needed. To avoid assessing mitigation strategies by simulating every building configuration, correlations of individual infection risk as a function of building mitigation parameters were developed upon extensive parametric studies.
... σ H is the turbulent Prandtl number. Therefore, unlike other simplified thermal models, the "degraded" momentum equations are either only air mass flows considered (Wang and Jin 1998;Wang and Chen 2007;Shan et al. 2020). For instance, the power law model (PLM) is based on the differential pressure driving force in the simplified Bernoulli equation (Dols and Polidoro 2020;Lu et al. 2020); or neglect the air mass flows between adjacent zones (mass transfer). ...
The temperature distribution is always assumed to be homogeneous in a traditional single-input-single-output (SISO) air conditioning control strategy. However, the airflow inside is more complicated and unpredictable. This study proposes a zonal temperature control strategy with a thermal coupling effect integrated for air-conditioned large-scale open spaces. The target space was split into several subzones based on the minimum controllable air terminal units in the proposed method, and each zone can be controlled to its own set-point while considering the thermal coupling effect from its adjacent zones. A numerical method resorting to computational fluid dynamics was presented to obtain the heat transfer coefficients (HTCs) under different air supply scenarios. The relationship between heat transfer coefficient and zonal temperature difference was linearized. Thus, currently available zonal models in popular software can be used to simulate the dynamic response of temperatures in large-scale indoor open spaces. Case studies showed that the introduction of HTCs across the adjacent zones was capable of enhancing the precision of temperature control of large-scale open spaces. It could satisfy the temperature requirements of different zones, improve thermal comfort and at least 11% of energy saving can be achieved by comparing with the conventional control strategy.
Electronic supplementary material esm:
the Appendix is available in the online version of this article at 10.1007/s12273-022-0942-8.
... Younes et al. 37 discussed the use of CFD, highlighting the fact that they are not suited for practical use and stated that the main CFD drawback is its computation time. Wang et al. 39 also explained that the use of CFD in practice is often limited by the computation time and calculation power necessary to obtain reliable models. ...
The airtightness of buildings has a significant impact on buildings’ energy efficiency, maintenance and occupant comfort. The main goal of this study is to provide an evaluation of the air leakage characteristics of dwellings in different regions in Canada. This study evaluated the key influencing factors on airtightness performance based on a large set of measured data (73,450 dwellings located in Canada with 11 measurement parameters for each). Machine learning models based on multivariate regression (MVR) and Random Forest Ensemble (RFE) were developed to predict the air leakage value. The RFE model, which shows better results than MVR, was used to evaluate the effect of the ageing of buildings. Results showed that the maximum increase in air leakage occurs during the first year after construction – approximately 25%, and then 3.7% in the second year, after which the increase rate becomes insignificant and relatively constant – approximately 0.3% per year. The findings from this study can provide significant information for building designs, building performance simulations and strengthening standards and guidelines policies on indoor environmental quality.
... One of the major drawbacks of using CFD methods is simulation time. In order to solve this problem, several methods have been proposed to reduce simulation time, such as the Multizone-CFD method [25] , FFD (fast fluid dynamics) method [26] , and GPU (Graphics Processing Unit)-FFD method [27] . ...
The air infiltration of buildings is closely related to its indoor and outdoor environment and energy consumption. However, measuring air infiltration of a building under natural conditions is time-consuming, easily affected and expensive, so it's often inferred based on building airtightness in practical engineering. Empirical models can nevertheless make a rapid prediction without building parameters, which are widely applied in practical engineering. At present, most of the existing empirical models take residential buildings as objects, therefore they are difficult to be applied to public buildings. Hence, it is imperative to build an empirical model applicable to public buildings. In this study, the conversion coefficients between the airtightness (air change rate under the pressure difference of 50Pa) and the air infiltration rates under natural conditions of four typical zones of public buildings were analyzed. Firstly, the airtightness of four zones of public buildings in the cold region of China was measured. Secondly, their air infiltration rates under 1800 combined conditions of wind pressure and stack effect pressure were simulated based on the airtightness measured results. Finally, calculation and statistical analysis of the conversion coefficient were carried out based on the measured and simulated results, and the recommended value of conversion coefficient was proposed. Analysis results show that the CC of each zone is significantly affected by outdoor meteorological conditions and varies in a wide range (1# zone: 3.21 to 188.44). It is advised to ignore the extreme data and take the mean value of the CC corresponding to 95% of the data volume as the recommended value (22.2). This study can provide theoretical basis for the formulation of standards for the performance evaluation of building airtightness.
... The calculation of the energy performance of a building is only accurate if the tightness of the building is measured [28,29]. It can be measured by various methods: theoretically [30,31], empirically [32][33][34][35][36], or by single-component models [37]. Relander et al. tested the tightness of connections between the basement wall and the wall with a wooden structure. ...
The aim of this work is to develop a model of heat supply to buildings with almost zero energy consumption, indicating the significant importance of heat losses and gains in heating installations. The prepared model is to indicate the need for changes in the structure and topology of heating installations, resulting from the changing heat demand of buildings. The need to create a new model is heightened by changes that relate to tightening legal regulations related to energy consumption and demand, which must meet the standards of buildings in Poland from 2021. The article presents the assumptions and results of analyses of the use of energy installations in residential buildings that use renewable energy sources to balance energy consumption in various areas of its use. To achieve this goal, calculations were made using simulations of the impact of the use of installations using renewable energy sources on the energy performance of a building with different quality of partitions and improvement of energy efficiency in accordance with the Polish standard PN-EN 12831. The test results allow to choose the most advantageous, from the point of view of economic profitability, option of replacing installations in residential buildings, and they also allow to determine the possibilities of meeting national obligations in the field of final energy reduction and increasing the share of renewable energy sources in meeting its demand in accordance with the EU obligations imposed on Poland. Thermomodernization of buildings in the temperate climate zone allows for a reduction of 38% of energy demand over the entire life cycle of a building and a reduction of CO2 emissions by 99%.
... The airtightness of and energy efficiency of the buildings can be determined by different methods [7]: theoretical investigation [8,9], empirical research [10,11], modelling of general building characteristics, or modelling of one component of the building [12]. The analysis of the related literature revealed that building energy performance calculations are precise only if building airtightness is defined by measurements. ...
The European Union has adopted legislation aimed to increase the use of renewable energy and improve the effectiveness of conventional-form energy use. Additional structure insulation helps to decrease heat energy loss. Airtightness of the building envelope (building airtightness) is an additional factor that determines comfortable and energy-saving living environment. The conformity of heat energy loss with the object's design energy class is one of the mandatory indicators used in the obligatory building energy performance certification procedure. Optionally, the objects to be certified are the entire buildings or separate units (flats). There is an issue of concern whether a flat assessed as a separate housing unit would meet the requirements of design energy class depending on the location of the unit in the building. The study is aimed to determine the change in heat loss of end units in terraced houses (townhouses) as a result of various factors, leading to uneven airtightness of the building envelope. The non-destructive assessment of building airtightness was implemented through the combined use of methods, namely Blower Door Test (around 200 measurements) and Infrared Thermography. The hollow clay unit masonry showed ca. 7-11% less airtightness than the sand-lime block masonry structure. The end units were up to 20% less airtight compared to the inside units.
... In such lines, the discharge coefficient for constant window openings is a fixed value of 0.6 but differs considerably with the window form in the case of operable windows (sash), the opening area, and the pressure difference across the opening [88]. CFD is a built-in hourly based building energy simulation model [89,90] and zonal airflow model [82] to obtain the more useful outcome and improve the accuracy of these simulations such as in DesignBuilder [91]. Under the CFD boundary, the importing EnergyPlus performance data can be viewed [92]. ...
This paper discusses the effect of various climatic conditions that pertain to passive design measurements and their relationships with building configurations to improve indoor thermal comfort based on the different climate zones in Egypt to support Egypt’s sustainability agenda 2030. We find the most appropriate design settings that can increase the indoor thermal comfort, such as building orientation and shape. These settings can be modeled using DesignBuilder software combined with Egyptian meteorological data. This software is used accompanied by computational fluid dynamics to numerically assess the outcomes of different changes, by simulating indoor climate condition factors such as wind speed and temperature. Natural ventilation simulations were performed for four different shapes to create comprehensive dataset scenarios covering a general range of shapes and orientations. Seven scenarios were optimized to put forward a series of building bioclimatic design approaches for the different characteristic regions. The results indicated that the temperature decreased by about 3.2%, and the air velocity increased within the study domain by 200% in the best and the worst cases, respectively, of the four different shapes. The results of the study gave evidence that the configuration of buildings, direction, and wind speed are very important factors for defining the natural ventilation within these domains to support the green building concept and the sustainable design for a better lifestyle.
... In the simplified approach followed by the present study, most components are modeled using the CONTAM multizone network program, and providing detailed CFD analysis only to a specific zone, where the simplified "well-mixed" assumption may not stand. This approach was possible thanks to Wang and Chen [6] who coupled CONTAM with CFD-0, a CFD code, originally developed by Srebric et al. [7], and improved [8]. ...
Naturally occurring radon gas represents the leading cause of lung cancer for nonsmokers. Limiting the amount of radon inhaled by residents is of utmost importance when designing homes and HVAC systems. The present paper focuses on dedicated 3D CFD simulations of indoor radon distribution in a dwelling located in Madrid, Spain, using the CONTAM and CFD-0 software developed by NIST. CFD can be easily used for indoor air flow analysis and reduces the mathematical limitations. The methodology presented includes all the necessary details for performing similar modelling of any dwelling. The results are qualitative and show the possibility to calculate detailed volumetric radon concentrations inside a ventilated dwelling using the CFD capabilities of CONTAM and having prior knowledge of the radon sources. Such simulations will allow a better estimate of the radon infiltration rate in order to mitigate the accumulation of radon inside dwellings.
... Usually, these models are based on homogenous indoor air and unformed temperature, neglecting airflow and because of that these assumptions can lead to an error. [8] Because of that, the CFD (computational fluid dynamics) methods are developed capable of reducing the number of assumptions needed for a multizone approach while still providing detailed airflow values, temperatures, and pollutant distribution conditions. Some of these simulations require complex mathematical apparatuses or long-time span, and as such are not adequate for small scale models and general implementation. ...
Infiltration has a considerable impact on both, energy efficiency and occupant comfort in buildings. Due to the complexity of the analysis of this phenomenon in buildings, the verification methods are very important for its diagnostics and evaluation. In this paper, the matter of infiltration in buildings is being considered referring to both, calculation models and methods, as well as through current standards and regulations in the EU and Serbia. Different valorization methods are presented and analyzed regarding their characteristics, applicability, and complexity. Finally, preliminary infiltration measurements with a pressurization test, conducted on selected buildings of Belgrade housing stock are presented and compared with values defined by the current regulations in Serbia. Results pointed out current problems and the need for improvements regarding the treatment of infiltration in local regulations and practice.
... CONTAM is an airflow and contaminant transport analysis software which is also extensively used for modeling fire smoke migration. Excellent agreement with experimental results can be obtained for some limited ranges of the temperature gradient [8], contaminant concentration gradient and momentum effect of airflows [9]. More accuracy can be added by using the CFD capability of COMTAM [10]. ...
Casualty of garment factory workers from factory fire in Bangladesh is a recurring tragedy. Smoke, which is more fatal than fire itself, often propagates through different pathways from lower to upper floors during building fire. Among the toxic gases produced from a building fire, carbon monoxide (CO) can be deadly, even in small amounts. This paper models the propagation and transportation of fire induced smoke (CO) that resulted from the burning of synthetic polyester fibers using two open source platforms, CONTAM and Fire Dynamics Simulator (FDS). Smoke migration in a generic multistoried garment factory building in Bangladeshis has been modeled using CONTAM where each floor is compartmentalized by different zones. The elevator and stairway shafts are modeled by phantom zones to simulate contaminant (CO) transport from one floor to upper floors. In this study, constant coefficient model of source and sink is used to find the extreme condition of fire and smoke propagation. It is kind of impossible to check the simulation project practically as it would involve testing full-scale fire in a garment facility. For this reason, two generic building structure resulting outputs are considered and comparative analysis and study is performed. Simulation method is operated based on “transient” contaminant flow, air flow. Transient integration method is performed based on Implicit Euler. FDS analysis involves burning of two different stacks of polyester jacket of six feet height and with a maximum heat release rate per unit area of 1500kw/m2 over a storage area 50m2and 150m2, respectively. The resulting CO generation and removal rates from FDS are used in CONTAM to predict fire-borne CO propagation in different zones of the garment building. “SFPE Handbook” is used as reference for the input values of fuel. Smokeview (SMV) is a support program used with Fire Dynamics Simulator to visually illustrate the code written in FDS. Real-time smoke propagation with time and space is displayed using SMV. In our study, two different types of fuel is used – Polyester and Cotton. For these fuels peak heat removal rate per unit area (HRRPUA), time of peak, smoke generation and removal rate are studied over a defined time period. For measuring smoke generation and removal rate, temperature of the room two separate devices is set within the smoke pathway. Findings of the study exhibit that the contaminant flow rate is a strong function of the position of building geometry, location of initiation of fire, amount of burnt material, presence of AHU and contaminant generation and removal rate of CO from the source location etc. In this study, source’s generation rate, removal rate, storage area of cloths, AHU supply and return rate, floor position are taken as variables. Varying these parameters smoke propagation in a multistory building is analyzed. The transport of fire-smoke in the building Hallways, stairways and lifts are also investigated in detail to examine the safe operation of the occupants in case of fire. Because using hallways smoke propagates from source room to other rooms of the floor and using phantom zone (stairways, lifts) smoke propagates to other floor of the building. That is why analysis of smoke propagation in hallways and phantom zone is given utmost importance in this study.
... The static coupling requires fewer resources and computational iterations and is more stable than quasi-dynamic and full dynamic couplings. Later, between 2007 and 2008, some authors (Wang and Chen, 2007a, 2007bWang and Wong, 2008) analyzed different methods for the information exchange between BES and CFD. The variables used in their study were pressure and airflow, which were exchanged differently between BES and CFD. ...
Building energy simulations coupled with computational fluid dynamics tools have emerged, recently, as an accurate and effective tool to improve the estimation of energy requirements and thermal comfort in buildings. Building modelers and researchers usually implement this coupling in the boundary conditions of both tools (e.g. surface temperature, ambient temperature, and conductive and convective fluxes). This work reviews how the building energy simulation–computational fluid dynamics coupling has evolved since its first implementation to the present day. Moreover, this article also summarizes and discusses the research studies in which the building energy simulation–computational fluid dynamics coupling has been used to analyze building systems, building components, and building urban configurations. Implementing a building energy simulation–computational fluid dynamics coupling brings a series of benefits when compared with the conventional building energy simulation methodology, a building energy simulation–computational fluid dynamics coupling provides an improvement that ranges between 10% and 50% for estimating the building energy requirements. Moreover, the computation time to implement computational fluid dynamics with information obtained from the building energy simulation could be reduced by as well.
... A coupled CFD and multi-zone program has been used to model the poorly mixed zones to avoid the errors and more impactful results. Wang and Chen (2007b) had validated the coupled multi-zone-CFD program by using experimental data. Results obtained with the coupled program had a good agreement with experimental data taken with non-uniform distributions of contaminant concentrations, air momentum effects and temperature. ...
The building provides shelter to live and most people spend their 85-90% time indoors. Therefore, it is quite important to ensure that the condition of the indoor environment is healthy for its living being. There are a number of methods to evaluate indoor air pollution of built spaces by performing experiments or doing it computationally. In this study, a review of computational studies carried out to evaluate the impact of different parameters like airflow pattern, indoor and outdoor contaminant concentrations etc., on indoor air quality (IAQ) of different type of buildings was done. Some commonly used software’s for the study of IAQ were also discussed.
... Compared with CFD simulation, the multi-zone network model program uses much less computational time. It usually only takes a few minutes or even seconds for a whole-building multizone analysis of smoke movement and therefore is increasingly used to study smoke spread in buildings (Liangzhu Wang & Chen, 2007. CONTAM (Dols & Polidoro, 2015) is the multizone program for building fire smoke analysis, which was also developed by NIST and is recommended by the ASHRAE Handbook of Smoke Control Engineering (Klote, Milke, Turnbull, Kashef, & Ferreira, 2012). ...
With rapid economic growth, the number of high-rise buildings increases significantly due to land shortage in highly populated cities. Compared with other types of buildings, high-rise buildings have a higher cooling load and are more energy intensive, leading to huge cooling energy consumption and peak electricity demand. Ventilation has proved to be an effective approach to reduce cooling load and thereby save cooling-related energy and reduce peak electricity demand for high-rise buildings, which is important for achieving sustainable development of cities and society. Building safety is a challenge in high-rise ventilation. Fires and the resultant air pollution in high-rise buildings are often disastrous and cause huge losses if the high-rise ventilation system is not designed and operated well. This paper presents a review of previous studies on energy efficiency and building safety for high-rise ventilation, including natural ventilation, mechanical ventilation and hybrid ventilation. Statistical analysis was conducted on the research methods, number of literature review sources, and topics. The research gap was also discussed. Through the review, it was found that increasing research has been conducted on high-rise ventilation, especially on the topic of building safety. It was also recommended to consider both safety and energy simultaneously, in order to achieve energy efficiency and safety in high-rise ventilation and therefore to promote the application of ventilation in high-rise buildings.
... SF6 and environmental tobacco smoke particle concentrations were released in the chamber and measurements compared with model predictions [16]. To obtain the detailed air flow and particle distribution in a specific zone, several researchers have integrated CFD with existing multizone models [17][18][19][20][21][22]. As another example, Gang Tan [23] developed a multizone coupled heat transfer and natural ventilation nodal model called multiVent. ...
The study of underground natural ventilation opportunities has become increasingly significant in recent years with its promise of wide application in underground structures such as underground hydro power stations, metro stations, underground parking and laboratories. It is recognized that deployment of natural ventilation constitutes a passive technology that can lead to significant energy conservation if applied judiciously. This paper focuses on underground buildings that are buried deeply and typically consist of an underground complex network of connected structures. The other characteristic is that these structures house machinery and devices that generate heat, leading to elevated internal air temperatures. Combined with the deep location, it implies that buoyancy forces are significant which make natural ventilation through vertical shaft openings a viable option. These characteristics demand a study of the heat transfer processes between ambient conditions, soil and underground buildings. In this paper, we present a dynamic flow network model with loops for multizone airflow and apply it to deep buried underground structures considering the dominant heat transfer characteristics, not only through the elements of the network but also the heat exchange with the envelope and adjacent soil mass. Finally, a small-scale experiment of occurring airflow is conducted and compared with the outcomes of the dynamic simulation of the proposed model. The comparison serves as validation and illustration of the application potential of the network model for natural ventilation investigation and consecutive optimization of its use in underground buildings.
... The field of building simulation (the study of ventilation and air quality in buildings) use coupled hybrid modellingthese instances involve the coupling of a "multizone model" (a 1D network model) and a field model [19,[54][55][56][57][58][59][60]. In building simulation, the field sub-model is typically used to simulate external wind conditions around the building and not features inside the building. ...
Systems in the built environment are getting bigger and more complex. Fire safety engineers are required to analyse these structures to ensure acceptable levels of safety. Computational limitations mean that the calculation domain must be curtailed. This ignores the two-way coupling between the total system and a fire. Coupled hybrid modelling (coupling of fire dynamics sub-models with a range of computational costs) expands the domain and analyses this two-way coupling within a reasonable timeframe. This article presents a literature review of this modelling paradigm and has application for those investigating and expanding the method.
Over the last quarter of a century, researchers have investigated coupled hybrid modelling but work has been in disconnected streams. There has been no review of coupled hybrid modelling for fire safety engineering. It is unclear where the knowledge gaps are and where future work should be focused.
This review demonstrates that the method is numerically feasible and can reduce wall clock time for total system analysis. This review reveals that there is limited validation and a host of unresolved questions (including sub-model choice, interface modelling, domain decomposition and coupling method). This review draws attention to the lack of collaboration which has led to obsolete models and parallel working.
This article shows that coupled hybrid modelling has potential but effort is being squandered. This review is a stepping-stone towards a standardised coupled hybrid framework. This review highlights where future collaborative research should be directed.
... The coupling procedure with CFD and airflow network model was investigated well by Wang and Chen. [37][38][39] They found that the coupling with static pressure will work well compared to that with airflow rate. The pressure coupling method uses the static pressure as the given boundary conditions for the CFD and flow network model. ...
This paper reviews computational fluid dynamics (CFD) analysis and simulation of a network model of airflow and transport scenarios, as well as their coupled simulation. The network model is a tool to describe the whole and macroscopic characteristics of airflow transport in buildings, where airflow is modeled as a network of one‐dimensional flow elements. The flow network model can be solved with comparatively less computational cost; however, all the airflows between nodes should be modeled as one‐dimensional. The airflows and their transports in a room are not one‐dimensional but three‐dimensional. CFD is a convenient tool for analyzing such three‐dimensional flows and transports. The equations are non‐linear, and their solutions are usually obtained numerically. The CFD analysis requires considerable computation resources and computational time. To analyze the whole and macroscopic characteristics of airflows and their transports in buildings including the space distribution features in a certain room, the two simulations should be carried out simultaneously. In this work, the author reviews the conduction of CFD in a room, network simulation in a whole building, and simulation of their coupling. Further, the author's previous works pertaining to this subject are explained.
... Firstly, a straightforward way is to apply CFD to the space where necessary and multizone models to the rest. Wang and Chen (2007) proposed to apply CFD to space existing non-uniform momentum and temperature distribution and multizone to the rest of the building. Based on this methodology, studied the control of VAV system by coupling BES, CFD, and multizone models. ...
This paper presents a comprehensive review of the open literature on motivations, methods and applications of linking stratified airflow simulation to building energy simulation (BES). First, we reviewed the motivations for coupling prediction models for building energy and indoor environment. This review classified various exchanged data in different applications as interface data and state data, and found that choosing different data sets may lead to varying performance of stability, convergence, and speed for the co-simulation. Second, our review shows that an external coupling scheme is substantially more popular in implementations of co-simulation than an internal coupling scheme. The external coupling is shown to be generally faster in computational speed, as well as easier to implement, maintain and expand than the internal coupling. Third, the external coupling can be carried out in different data synchronization schemes, including static coupling and dynamic coupling. In comparison, the static coupling that performs data exchange only once is computationally faster and more stable than the dynamic coupling. However, concerning accuracy, the dynamic coupling that requires multiple times of data exchange is more accurate than the static coupling. Furthermore, the review identified that the implementation of the external coupling can be achieved through customized interfaces, middleware, and standard interfaces. The customized interface is straightforward but may be limited to a specific coupling application. The middleware is versatile and user-friendly but usually limited in data synchronization schemes. The standard interface is versatile and promising, but may be difficult to implement. Current applications of the co-simulation are mainly energy performance evaluation and control studies. Finally, we discussed the limitations of the current research and provided an overview for future research.
... In the mixing ventilation, air speed increases if the airflow rate grows, furthermore, near the air inlet are higher, meanwhile in the occupied zone are smaller air speed. As computer sciences developed, more researchers applied CFD for room airflow investigations (Srebic 2010;Wang and Chen 2007;Yongsona et al. 2007) numerically investigated the room airflow and air speed distribution in the occupied zone of a room. Goda (2010Goda ( , 2014 numerically and experimentally investigated the air speed and air temperature distribution in a tangential air-distribution system. ...
The purpose of this paper is to investigate the influence of air change number on the airflow homogeneity in a single office full-scale model room, where tangential air distribution system was used. Air speed, turbulence intensity and air temperature measurements were performed. Then different statistical methods were applied to evaluate the airflow homogeneity. Results showed that the average of turbulence intensity was independent of the air change number at ankle, knee heights, and head height of seated and head height of standing person. The draught rate numbers were calculated to evaluate the discomfort due to draught using Fanger's model and its maximum value was independent of the air change number. The draught at ankle height was within category A, while at the other heights was within category B and C. The transformed distribution function of the measured air speed was created in each measurement point to describe the airflow homogeneity. Results showed that the airflow was homogenous at ankle height. At knee height and head height of seated and standing person, the fluctuation tendency of air speed was the same. Our results could help designers to predict the airflow homogeneity in a tangential air distribution system for room air distribution.
... CONTAM is an airflow and contaminant transport analysis software which is also extensively used for modeling fire smoke migration. Excellent agreement with experimental results can be obtained for some limited ranges of the temperature gradient [8], contaminant concentration gradient and momentum effect of airflows [9]. More accuracy can be added by using the CFD capability of COMTAM [10]. ...
Casualty of garment factory workers from factory fire in Bangladesh is a recurring tragedy. Smoke, which is more fatal than fire itself, often propagates through different pathways from lower to upper floors during building fire. Among the toxic gases produced from a building fire, carbon monoxide (CO) can be deadly, even in small amounts. This paper models the propagation and transportation of fire induced smoke (CO) that resulted from the burning of synthetic polyester fibers using two open source platforms, CONTAM and Fire Dynamics Simulator (FDS). Smoke migration in a generic multistoried garment factory building in Bangladesh is modeled using CONTAM where each floor is compartmentalized by different zones. The elevator and stairway shafts are modeled by phantom zones to simulate contaminant (CO) transport from one floor to upper floors. FDS analysis involves burning of two different stacks of polyester jacket of six feet height and with a maximum heat release rate per unit area of 1500kw/m² over a storage area 50m² and 150m², respectively. The resulting CO generation and removal rates from FDS are used in CONTAM to predict fire-borne CO propagation in different zones of the garment building. Findings of the study exhibit that the contaminant flow rate is a strong function of the position of building geometry, location of initiation of fire, amount of burnt material, presence of AHU and contaminantgeneration and removal rate of CO from the source location etc. The transport of fire-smoke in the building Hallways, stairways and lifts are also investigated in detail to examine the safe egress of the occupants in case of fire.
... where is the discharge coefficient normally ranging between 0.6 to 0.75; is the area size of the opening; is the density of the air; is constant, which is 0.5 for large openings. Δ is the pressure difference consisting of total pressure difference , pressure difference due to wind Δ , and pressure difference due to density and elevation difference Δ (Wang and Chen 2007). ...
Multizone models are widely used in building airflow
and energy performance simulations because they are
often suitable for the analysis needed, and due to their
fast computation speed. However, the results provided
by the multizone models are sometimes limited due to
the underlying well-mixed assumption of the air in a
zone (e.g., a room). For zones where this assumption is
not suitable, a Computational Fluid Dynamics (CFD)
models may be needed. This paper proposes a coupled
simulation model between the multizone and CFD
model, which in the paper is fast fluid dynamics, a freely
available and publicly released program. The model
allows the simulation of a dynamic interaction between
airflow and Heating, Ventilation and Air-Conditioning
(HVAC) systems for buildings with stratified airflow
distribution in some of the zones. The approach is
implemented using Modelica and its buildings library.
In this presentation, we first discuss the design and
implementation of a data synchronization strategy
between the two models. We then show a possible
validation of the implementation by comparing the
simulated results with experimental data from previous
research. Finally, we perform a case study by linking a
Variable Air Volume (VAV) terminal box to space in
order to evaluate the capability of the coupled
simulation. Finally, further research needs are discussed
at the end of the paper.
... Multizone networks are simplified models, neglecting momentum effects and temperature distributions within a zone [87], but are the only acceptable option for airflow simulation in whole medium-to-large buildings [88]-let alone 50,000 annual simulations. Multizone networks have been validated [53,89,90], and their predictions for bulk airflow rate are rarely worse than about 30% [91,92], a level that has been found to have negligible impact on indoor temperature [93]. They have been used extensively in infiltration and natural ventilation studies [94][95][96][97]. ...
This work develops guidance and tools to understand the performance, improve the design, and simplify the evaluation of naturally ventilated low-rise commercial buildings in warm and hot climates. We conducted ~50,000 detailed energy and airflow simulations in 427 locations across Brazil, varying 55 parameters representing building morphology, fenestration, construction properties, internal gains, operating times, wind modifiers, flowpaths, window control, and soil traits. Comfort performance was quantified by the average annual fraction of occupied hours that exceeded the upper limit of an adaptive comfort zone, and investigated with sensitivity analysis and machine learning methods. Results indicated that, after climate, building size (both footprint area and number of stories) and internal gains were most influential and were positively associated with discomfort. Adding air movement with ceiling fans and providing for night ventilation both proved highly effective comfort interventions. Except for roof solar absorptance, opaque envelope changes, including increasing insulation or thermal mass, had only marginal impacts. A support vector regression metamodel, requiring 29 easily obtainable inputs plus a weather file, was fit to the simulation results and successfully validated (R2 = 0.97). The metamodel was developed as a simplified compliance path for naturally ventilated buildings to enhance Brazil's commercial building performance labeling program, which, because it currently provides such a path only for air conditioned buildings, may discouraging decision-makers from considering even more efficient passive solutions. We use a case study to show how the metamodel, which we will distribute publicly, can also serve as a design tool, and demonstrate that modifying a small set of parameters can drastically improve thermal performance and achieve sustainable comfort in hot and warm climates.
The dispersion prediction model called CONTAM has been widely used to predict airflow rates in multi-zone indoor environments. However, as CONTAM adopts the lumped system approach under the assumption that the air in each room is well mixed, and thus the pressure and temperature are homogeneous, its prediction may be inaccurate in certain cases. Thus, this study proposed an efficient algorithm that yielded improved flow rates by reflecting the non-uniform distribution of pressure or the presence of dynamic pressure based on single-zone computational fluid dynamics. The proposed method selectively applied a large-eddy simulation to obtain information on velocity, pressure, and temperature, which can be used for the accurate prediction of flow rates across multi-zone environment.
The Qinghai-Xizang Plateau is characterized by a low-pressure and oxygen-deficient environment due to its high altitude, causing discomfort and major safety problems for the inhabitants. To address this, oxygen-enriched chambers can be used to alleviate the plateau reaction. However, little consideration has been given to air infiltration in these chambers, with a lack of information on the corresponding infiltration heat loss phenomenon. This paper addresses this by investigating the phenomenon of air flow in an oxygen-enriched chamber using experiments and simulations. The results highlight that when there is a difference in oxygen concentration between the interior and exterior of the chamber, mass transfer occurs due to both the molecular diffusion in addition to a flow due to the air density difference caused by the variation in concentration. Also, the simultaneous stack effect is roughly equivalent to 10 times the oxygen pressure, and the two pressure effects act in opposite directions. It is also noted that both the oxygen pressure and the stack effect decrease as the atmospheric pressure decreases. Overall, the oxygen-enriched chambers exhibit less infiltration in plateau areas with a low atmospheric pressure compared to plains areas with a relatively high atmospheric pressure. Finally, this study establishes formulas that can be used to calculate air infiltration rates in oxygen-enriched chambers. This study fills a gap in the existing literature regarding the air infiltration mechanism in oxygen-enriched chambers at high altitudes and low pressures, providing a theoretical foundation for improving indoor environments in the Qinghai-Xizang Plateau and other high-altitude regions.
The airtightness of buildings is continuing to grow and impact the indoor environment. Its aim is to conserve energy, but this may influence the indoor air quality and increase contaminant accumulation by limiting the amount of fresh air that infiltrates the building. The goal of this study was to quantify how the contaminants from a faulty gas furnace in a household could impact the occupants. The gas furnace was located in an attached garage and leaked carbon monoxide (CO). Multizone and CFD simulations were caried out to determine if an air terminal device (ATD) with a changing geometry could improve the air quality. The goal of the ATD was to maintain a steady air throw in the garage, while the air flow in the ventilation system would change. A steady air throw should help to remove the carbon monoxide generated from the furnace and prevent infiltration into the household. The results show that with the use of the new ATD, it was possible to maintain a steady air throw and the infiltration of CO was lowered.
Control of the indoor environment in buildings is reactive and usually based on sensor data at a single location in a room without any consideration of the air flows within the space. The ability to accurately simulate indoor conditions would enable predictive control offering improved environmental conditions and better energy efficiency. This study investigates the temporal prediction of temperature and its coupling with sensor data for improving thermal comfort forecasting in an indoor environment. We present a real-time implementation of a computational fluid dynamics (CFD) Lattice Boltzmann method (LBM) model coupled with data assimilation (DA) to make periodic updates to the state of the model. Variational and sequential DA techniques are evaluated and two novel methods for real-time accurate temperature prediction are presented. The models are demonstrated for prediction of temperature in an idealised room, with simulated temperature sensor readings used to update LBM-based flow predictions. The LBM-DA approach overcomes the need for accurate boundary conditions while considerably improving the transient and spatial prediction of temperature in terms of root mean squares error, thereby avoiding large deviation from the room’s true flow state. The accuracy of prediction is shown to depend on number of sensors with poor prediction using just a single sensor. Results also depend on quality of sensor data, with highly variable data yielding poorer results. The approach has potential for application in indoor environments to provide more accurate and faster response of control systems to changing environmental conditions.
Natural ventilation has been used widely in buildings to deliver a healthy and comfortable indoor environment for occupants. It also reduces the consumption of energy in the built environment and dilutes the concentration of carbon dioxide. Various methods and techniques have been used to evaluate and predict indoor airspeed and patterns in buildings. However, few studies have been implemented to investigate the relevant methods and tools for the evaluation of ventilation performance in indoor and outdoor spaces. The current study aims to review available methods, identifying reliable ones to apply in future research. This study investigates scientific databases and compares the advantages and drawbacks of methods including analytical models, empirical models , zonal models, and CFD models. The findings indicated the computational fluid dynamics (CFD) model is the most relevant method because of cost-effectiveness, informative technique, and proficiency to predict air velocity patterns and ratios in buildings. Finally, widely used CFD codes and tools are compared considering previous studies. It is concluded the application of codes for research is subject to the complexity and characteristics of a studied model, the area and field of study, the desired turbulence model, and the user interface.
In Central and Eastern Europe, a growing popularity of gas heaters as the main source of heat and domestic hot water can be observed. This is the result of new laws and strategies for funding that have been put in place to encourage households to stop using coal and replace it with cleaner energy sources. However, there is a growing concern that gas furnaces are prone to malfunction and can be a threat to occupants through CO (carbon monoxide) generation. To see how a faulty gas furnace with a clogged exhaust may affect a household, a series of multizone and computational fluid dynamics (CFD) simulations were carried out using the CONTAM software and CFD0 editor created by the National Institute of Standards and Technology (NIST). The simulations presented different placements of the furnace and ventilation outlet in an attached garage. The results showed how the placement influenced contaminant migration and occupant exposure to CO. It changed the amount of CO that infiltrated to the attached house and influenced occupant exposure. The results may be used by future users to minimize the risk of CO poisoning by using the proper natural ventilation methods together with optimal placement of the header in the household.
This work describes a deep learning methodology for “emulating” temperature outputs produced by the Fire Dynamics Simulator (FDS), a CFD software. An array of artificial neural networks (ANNs) is trained to predict transient temperatures at specified locations for a transient heat release rate (HRR) input. These locations correspond to the locations of thermocouples used in an experimental burn structure. In order to build the training set, A Gaussian process (GP) framework is used to develop a generative model that produces random viable HRR ramps. Although this procedure may require thousands of FDS runs to build a sufficient training set, the application of transfer learning can reduce the required number of runs by nearly an order of magnitude. This refers to the process of initially training an ANN to predict the output of the Consolidated Model of Fire and Smoke Transport (CFAST) and then transferring its knowledge to an ANN that learns to predict FDS outputs. CFAST is a much faster model than FDS, so a large training set can be generated quickly. The final state of the ANN trained to emulate CFAST is used as the initial state of an ANN that learns to emulate FDS. The result is a model that produces FDS temperature predictions with a mean absolute error (MAE) of less than 2°C and runs over five orders of magnitude faster than FDS. The emulators are also capable of learning inverse mappings; i.e. for a given temperature output, they can predict the HRR ramp that would cause FDS to produce the temperature response. This ability to invert for the HRR profile is exercised on data collected from eight fire experiments with peak HRRs up to 200 kW, including four propane burner fires, two methanol pool fires, and two n-Hexane pool fires. The model inverts for the experimental HRR with a MAE of 5.8 kW-15.4 kW (11.3%–16.7%) for the burner tests and 5.0 kW–25.5 kW (12.1%–28.6%) for the pool fire tests, with a tendency to underestimate the HRR of the pool fires. Finally, the computational speed of the emulators allows for the incorporation of CFD physics in Bayesian parameter inversion. As an example, this is demonstrated to infer the radiative fraction from experimental and synthetic data in conjunction with reported uncertainties from the FDS Validation Guide.
Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. 1.-RADON Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead and various other short-lived radioactive elements; radon itself is the immediate decay product of radium. Its most stable isotope, 222 Rn, has a half-life of only 3.8 days, making radon one of the rarest elements since it decays away so quickly. However, since thorium and uranium are two of the most common radioactive elements on Earth, and they have three isotopes with very long half-lives, on the order of several billions of years, radon will be present on Earth long into the future in spite of its short half-life as it is continually being generated. The decay of radon produces many other short-lived nuclides known as radon daughters, ending at stable isotopes of lead
1.-RADON Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead and various other short-lived radioactive elements; radon itself is the immediate decay product of radium. Its most stable isotope, 222 Rn, has a half-life of only 3.8 days, making radon one of the rarest elements since it decays away so quickly. However, since thorium and uranium are two of the most common radioactive elements on Earth, and they have three isotopes with very long half-lives, on the order of several billions of years, radon will be present on Earth long into the future in spite of its short half-life as it is continually being generated. The decay of radon produces many other short-lived nuclides known as radon daughters, ending at stable isotopes of lead 2.-CONTAM CONTAM, and other multizone modeling programs, can be useful in a variety of applications to analyze building airflows, pressure differences and contaminant transport. Its ability to calculate building airflows is useful in assessing building air change rates, interzonal airflow rates and comparing ventilation strategies. The analysis of pressure relationships between building zones is particularly useful in analyzing smoke control systems. The contaminant transport simulation capabilities of CONTAM can be useful for performing indoor air quality (IAQ) analysis including IAQ design, contaminant source isolation, IAQ forensics and
The study of buoyancy ventilation in underground buildings is crucial for the purpose of temperature control and smoke extraction. Some underground spaces have unique properties such as their deep location, with installed vertical channels of several hundred meters in length, raising the potential to rely on buoyancy driven ventilation only. This paper studies a particular phenomenon in such deep spaces with high intensity heat sources, e.g. power generating turbines. The phenomenon studied in this paper concerns the way that different steady states of flow and temperature can establish themselves. They are studied through an experimental set up and numerical simulations. Multiple factors, like the initial condition, the intensity and location of the heat source, are investigated, in particular to find how the final steady states in different situations are reached. It is well understood that the dominant flow tends to follow the expansion of the local thermal plume. An initial velocity may however alter this trend and an alternative steady state can be reached but this depends on the magnitude of the initial velocity. The critical initial velocity for the transition among these steady states is therefore studied in detail. However, once the steady solution is reached, this is not dependent on the initial velocity or other conditions. Thermal buoyancy pressure of fluid flow is generated by gravity forces due to density difference. Buoyancy forces work together with other forces (such as mechanical fans which have a given location and direction, and wind pressures over openings) to result in natural ventilation flows in spaces with openings that connect with outside air. The multi-steady-states of fluid flow in an underground space is determined by the fundamental characteristic of thermal buoyancy pressure and its understanding and predictability is crucial to be able to predict temperatures and natural ventilation flows correctly.
Hospital and laboratory buildings are designed with intrinsic features for infection control, and are related to an intensive energy use. Although many studies suggest that insufficient ventilation increases the risk of disease transmission in the indoor environment, significant questions still remain on the ventilation requirements for airborne infection control. ASHRAE proposes high research priority on the study of indoor flow regimes, room pressurization and filtration, for hospitals and laboratories where infectious diseases agents are handled. The objective of this paper is to promote an assessment and validation of the CFD-0 module of the CONTAM software, for the simulation of airborne contaminant transport in hospital and laboratory applications. These objectives are justified by the fact that this public domain code, supported by the NIST, may be an important tool for studying the role of ventilation parameters in infection control for hospital and laboratory settings. Three benchmarks were selected for that task: the ASHRAE-RP 1271, geared to challenge the code ability in simulating the complex indoor airflow features, such as jets, separation, impingement, and thermal plumes, that arise in room transitional non-isothermal confined flow; A benchmark that resembles real laboratory spaces; and a third benchmark, that resembles real hospital isolation rooms. Results demonstrated that CFD-0 provided, at least, a marginally acceptable performance, for mixed and displacement ventilation modes. The prediction results are more meaningful than those using the “perfect mixture” assumption, for assessments on ventilation performance and personnel exposure to hazardous substances in these spaces.
In recent decades there has been a growing awareness regarding energy consumption in buildings. Unfortunately, at a time when all building actors should get involved in the challenge to reduce energy consumption, designers cannot rely on effective tools to help them in their decision making process concerning airtightness. This literature review allows the identification of two important issues: new airtightness predictive models are complex to develop and existing airtightness predictive models do not meet the needs of designers and contractors. This paper is divided into three main parts in addition to the introduction and the conclusion. The first part deals with the key concepts of infiltration and airtightness, the second part with influencing factors and the third part with airtightness predictive models. These different chapters highlight a need for standardization regarding the metrics used for data presentation, parameters definition and statistical quantification. The lack of standardization hinders the development of a new airtightness predictive tool for designers and contractors. Along with the problem of standardization, supervision and workmanship are parameters that are difficult to model. Their significant impact can explain why designers and contractors find some existing models unreliable. This paper concludes that none of the existing models can be used in their present form as design tools. Further work should focus on the standardization of data presentation and on the development of a new airtightness predictive model. The first step in the development of such a model is to draw an appropriate classification of “air paths.”
Natural ventilation represents one of the challenges in green buildings design since the most important parameter that reflects the quality of building design is the thermal comfort within the indoor environment. This paper introduces experimental and numerical investigations for evaluating the impacts of natural ventilation on the thermal comfort inside residential buildings. Computational Fluid Dynamics (CFD) simulations were carried out to assess the wind environment within the study domain. Then, the solved flow field was used to calculate the temperature field. Validation of the simulation results was performed using experimental measurements. The parameters considered in the study were the air velocity, relative humidity, and the dry bulb air temperature. The study results show that there are significant thermal discomfort conditions inside the study domain, due to the lack of air circulation within the domain as a result of the building geometry. Accordingly, the obtained results reflect the need for design modifications in window parameters (window size, window placement, and shades) to improve the thermal comfort within the domain. Applying the design modifications led to a decrease in the air temperature by 2.5% and an increase in the air velocity within the study domain by six times.
The airflow in buildings involves a combination of many different flow elements. It is, therefore, difficult to find an adequate, all-round turbulence model covering all aspects. Consequently, it is appropriate and economical to choose turbulence models according to the situation that is to be predicted. This paper discusses the use of different turbulence models and their advantages in given situations. As an example, it is shown that a simple zero-equation model can be used for the prediction of special situations as flow with a low level of turbulence. A zero-equation model with compensation for room dimensions and velocity level also is discussed. A k-ε model expanded by damping functions is used to improve the prediction of the flow in a room ventilated by displacement ventilation. The damping functions especially take into account the turbulence level and the vertical temperature gradient. Low Reynolds number models (LRN models) are used to improve the prediction of evaporation-controlled emissions from building material, which is shown by an example. Finally, large eddy simulation (LES) of room airflow is discussed and demonstrated.
This paper reviews empirical validation studies of the application of multizone indoor air quality (IAQ) models to residential-scale buildings. This review focuses on empirical verification efforts, although models have also been subjected to analytical verification and inter-model comparisons. In most reports, experimental data were compared to predictions of only one model - typically, either the CONTAM or COMIS models. However, inter-model comparisons have demonstrated consistency between these and other multizone models so most comparisons can be generalized to all multizone models. Few of the empirical verifications reported statistical analyses of the comparison between measurements and predictions. Where sufficient data were available in the literature, additional statistical analyses have been performed and reported. Also, most published reports did not address the issue of measurement uncertainty. No single reported multizone IAQ model validation effort can be considered to be complete due to limitations in scope, inadequate detail describing experimental and/or modeling procedures, lack of rigorous statistical analysis, inclusion of only small ranges of airflows and concentrations, questions on independence of validation datasets, and other shortcomings. However, if one considers the body of published validation work, it may be concluded that a knowledgeable user can expect to make reasonable predictions of air change rates, interzonal flows, and contaminant concentrations for residential-scale buildings dominated by stack-driven or ventilation flows with inert pollutants. In contrast, more work is clearly needed for applications with high wind speeds, reactive contaminants, or specialized situations such as ambient pollutant entry, small time scales, and non-trace contaminants. Additionally, future model validation efforts will be more useful if more statistical analyses are performed and if more detail on both the measurements and modeling are reported.
Neutron interferometry has proved to be a very precise technique for measuring the quantum mechanical phase of a neutron caused by a potential energy difference between two spatially separated neutron paths inside interferometer. The path length inside the interferometer can be many centimeters (and many centimeters apart) making it very practical to study a variety of samples, fields, potentials, and other macroscopic medium and quantum effects. The precision of neutron interferometry comes at a cost; neutron interferometers are very susceptible to environmental noise that is typically mitigated with large, active isolated enclosures. With recent advances in quantum information processing especially quantum error correction (QEC) codes we were able to demonstrate a neutron interferometer that is insensitive to vibrational noise. A facility at NIST’s Center for Neutron Research (NCNR) has just been commissioned with higher neutron flux than the NCNR’s older interferometer setup. This new facility is based on QEC neutron interferometer, thus improving the accessibility of neutron interferometry to the greater scientific community and expanding its applications to quantum computing, gravity, and material research.
The potential for using a large eddy simulation (LES) computational fluid dynamcis (CFD) model to analyze builidng indoor air quality (IAQ) and ventilation problems was investigated. The LES model was developed by the Fire Science Division of NIST to simulate the transport of smoke and hot gases during a fire in an enclosure. Based on an extensive literature review, the application of the LES model to a test case, and discussions with building industry contacts, it was determined that this model offers unique capabilities compared to other available CFD models and could be used to make a significant contribution in studying issues of current interest in the IAQ and ventilation field. Recommendations for future work include evaluation of the predictive accuracy of CFD, analysis of topics that take advantage of transient simulation capability of this model, and development of a strategy for U.S. industry to apply CFD in the design process.
This paper describes the implementation of a computational fluid dynamic algorithm within the ESP-r building energy modelling system. While the implementation is specific to ESP-r, the conflation approach is general and could be applied to other building performance appraisal programs. The paper also presents an example application to indicate the potential effects of the enhanced modelling resolution and some of the new issues to emerge. INTRODUCTION Building energy/environmental prediction based on computational modelling is receiving much attention at the present time: mathematical models, discretisation techniques and numerical methods are being refined, and application knowhow is maturing. Building simulation (BSim), in which the building's distributed capacity and air volumes are discretised (the latter relatively crudely), and computational fluid dynamics (CFD), in which some fluid domain is finely discretised, are two significant development fields. BSim conceives of a build...
Many indoor air quality (IAQ) studies use multizone airflow analysis and computational fluid dynamics (CFD) simulation. Multizone analysis needs little computing time, but assume uniform air distribution in each zone. CFD can provide field distribution for each zone but is very computationally demanding. The present study attempted to integrate the two programs together to take their advantages by using three coupling strategies. Virtual coupling uses CFD simulation results to provide boundary conditions for CONTAM. Quasi-dynamic strategy improves the discharge coefficients in CONTAM based on CFD simulation. Dynamic coupling uses CONTAM to provide flow/pressure boundary conditions for CFD and improves the discharge coefficient in CONTAM by using CFD results. Preliminary results show that all the three coupling schemes can result in more reliable airflow patterns. Further investigations are needed to improve the coupling procedures and apply to more complex cases.
Multizone models are a common tool for calculating air and contaminant exchange within the rooms of a building and between a building and the outdoors. Usually a whole room is modeled by one calculation node with the assumption of homogeneously mixed conditions within this room, but in real cases, temperature and contaminant concentrations vary in space. The exchange to neighboring nodes via flow paths is a function of the local values of these variables. Detailed knowledge can be obtained from the solution of the transport equations for the airflow pattern (computational fluid dynamics, CFD) within the room at the expense of far higher computation cost. This work shows how results from CFD calculations can enhance the accuracy of multizone model predictions to give a better description of real cases. Parameter transfer between a multizone program and a detailed airflow simulation program is discussed. The method is then applied to example cases with air in/exfiltration, ventilation, and contaminant propagation and flow through large openings and shows its ability for a more accurate prediction of the contaminant spread. In the cases shown, concentration values differ by up to a factor of 2.5 from the purely multizonal approach. In the case with open windows, the multizonal prediction is 0.12 ppm for the concentrations in a neighboring room, whereas the corresponding values of the new method vary between 0.05 and 0.23 ppm for different source positions.
Presents introductory skills needed for prediction of heat transfer and fluid flow, using the numerical method based on physical considerations. The author begins by discussing physical phenomena and moves to the concept and practice of the numerical solution. The book concludes with special topics and possible applications of the method.
Understanding airflow in buildings is essential for improving energy efficiency, controlling airborne pollutants, and maintaining occupant comfort. Recent research on whole-building airflow simulation has turned toward protecting occupants from threats of chemical or biological agents. Sample applications include helping design systems to reduce exposure, and selecting optimal sensor locations. Multizone models and computational fluid dynamics (CFD) provide complementary approaches to predicting airflows in buildings. Multizone models treat a building as a collection of well-mixed zones, connected by flow paths such as doors, windows, etc. These zone-to-zone airflows carry contaminants around the building. However, the multizone formulation assumes that pollutants mix perfectly and instantaneously within each zone. For large spaces that take a long time to mix, these models cannot assess occupant exposures, or guide decisions about sensor placement or ventilation strategy. Furthermore, since the airflow in most large spaces couples tightly to the rest of the building (through doors and ventilation systems), errors due to neglecting the room details eventually propagate to the rest of the solution.
A simple treatment of computational fluid dynamics and heat transfer (usually abbreviated as CFD) is presented in this article. The authors have intentionally avoided the more advanced concepts such as mesh adaptivity or parallel processing (Ladeinde, 1992), and have limited the examples to very simple, albeit useful, systems. They will define CFD and describe the questions answered by CFD results and the advantages and limitations of the approach compared to physical experiments. They will then discuss the growing popularity of CFD and existing industrial applications in mechanical engineering. The obvious applications of this technique in the HVAC and R industry are presented prior to the conclusion of this article.
The design of an indoor environment requires a tool that can quickly predict the three-dimensional distributions of air velocity, temperature, and contaminant concentrations in the room on a desktop computer. This investigation has tested a zero-equation turbulence model for the prediction of the indoor environment in an office with displacement ventilation, with a heater and infiltration and with forced convection and a partition wall. The computed air velocity and temperature distributions agree well with the measured data. The computing time for each case is less than seven minutes on a PC Pentium II, 350 MHz.
Abstract Current guidelines for green buildings are cursory and inadequate for specifying materials and designing ventilation systems to ensure a healthful indoor environment, i.e. a "healthy building," by design. Public perception, cultural preferences, litigation trends, current codes and regulations, and rapid introduction of new building materials and commercial products, as well as the prevailing design-build practices, pose challenges to systems integration in the design, construction and operation phases of modern buildings. We are on the verge of a paradigm shift in ventilation design thinking. In the past, thermal properties of air within a zone determined heating, ventilating, and air-conditioning specifications. In the future, occupant-specific and highly responsive systems will become the norm. Natural ventilation, displacement ventilation, and microzoning with subfloor plenums, along with the use of point-of-source heat control and point-of-use sensors, will evolve to create a "smart," responsive ventilation-building dynamic system. Advanced ventilation design tools such as the modeling of computational fluid dynamics (CFD) will be used routinely. CFD will be integrated into air quality and risk assessment models.
To facilitate multi-variate performance appraisal all aspects of a building must be treated simultaneously. This paper gives examples of how the principal technical domains relating to a building’s environmental performance are coupled within the ESP-r integrated simulation package. Essentially, the equation-sets defining each domain are processed by customised solvers, while the domain interactions are handled by ensuring that the equation-sets for a given domain are established and solved as a function of information defining the evolution of any coupled domains. An earlier version of this paper appears in the proceedings of Building Simulation’99 [J.A. Clarke, Proc. Building Simulation’99, 1999] [1].
Multizone network models employ several assumptions, such as uniform pressure and quiescent air inside the zone, which may cause inaccurate results in flow calculations. This study intended to eliminate these assumptions in the zones, where these assumptions are inappropriate, by coupling a multizone network program with a CFD program. Through theoretical analysis, this paper proves that the solution of a building air distribution simulation by using the coupled program exists and is unique. Three possible coupling methods are then discussed and the best one is identified by studying their convergence and stability characteristics. A numerical test is further performed to verify the theory and it shows that the coupled program is able to effectively improve the accuracy of the results.
Light wells in the centers of high-rise apartment buildings in Japan are called ‘Voids’. Gas water-heaters built into Voids discharge exhaust gas so a large enough opening has to be designed at the bottom of a Void to keep the indoor air quality (IAQ) acceptable. In order to secure the IAQ in the Void from contamination, a simple calculation method of the ventilation rate induced by wind force and thermal buoyancy through openings at the bottom, along with heat sources such as water-heaters, is presented. The accuracy of this calculation method was examined by wind tunnel testing. As a result, it turned out that the simple calculation methods introduced in this study were valid for predicting the vertical temperature distribution and ventilation rates in Voids.
Advanced heat and flow models (as employed within Building Thermal and Mass Flow Simulation (BSim) and Computational Fluid Dynamics (CFD)) with different degrees of detail were investigated and their modelling deficiencies identified. The CFD technique, which defines the fluid flow on a ‘micro’ scale, was integrated into BSim in which fluid flow is described in a larger scale. The resulting combined approach strengthens the modelling potential of each methodology by overcoming their specific deficiencies. BSim's inability to predict air flow property gradients within a single space was surmounted and the difficulty of estimating CFD boundary conditions are now supplied by BSim. The conflated methodology allows the analysis of part of the building via a detailed CFD technique where air property gradients are judged to be crucial while in the rest of the building, where the air can be considered mixed, less resolved BSim approach is employed. The BSim environment, ESP-r, was elected to perform the current work. Two air flow situations encountered within buildings are discussed to demonstrate the combined method's applicability when compared with the BSim approach. Finally, general conclusions are presented showing that the developed methodology is very promising.
A validation study of the airflow and contaminant migration computer model CONTAM as applied to tall buildings. The Pennsylvania State University
- R Upham
Upham, R. 1997. A validation study of the airflow and contaminant migration computer model CONTAM as applied to tall buildings. The Pennsylvania State University, University Park, Pennsylvania.
Effective prediction of air distribution and contaminant transport in entire buildings by coupling multizone, CFD and energy models
- J Yuan
- Yuan J.
Yuan, J. 2003. Effective prediction of air distribution and contaminant transport in entire buildings by cou-pling multizone, CFD and energy models. Master's thesis, The Pennsylvania State University, Univer-sity Park, Pennsylvania. Downloaded by [Monash University Library] at 23:50 07 March 2015
The international Building Performance Simulation Association
- Madison Conference
- Wisconsin
- Usa
- Ibpsa
Conference, Madison, Wisconsin, USA, IBPSA (The international Building Performance
Simulation Association).
CONTAMW 2.1 User Manual
- G N Walton
- W S Dols
- Walton G. N.
Walton, G. N. and W. S. Dols. 2003. CONTAMW 2.1 user manual. Gaithersburg, MD, USA:
National Institute of Standards and Technology.
Airpak user manual, Fluent Inc. and ICEM-CFD Engineering
- Fluent
Fluent. 2002. Airpak user manual, Fluent Inc. and ICEM-CFD Engineering.
Use of computational fluid dynamics to analyze indoor air quality issue Gaithersburg, MD : National Institute of Standards and Technology
- S J Emmerich
- Emmerich S. J.
A validation study of the airflow and contaminant migration computer model CONTAM as applied to tall buildings
- R Upham
- Upham R.